Time Zones

Davis Treybig
Five Guys Facts
Published in
8 min readJul 8, 2017


We think of time zones as simple things, but in fact they are very, very complicated.

Before we get into some of the world’s crazy time zones, let’s start with a brief history lesson. Long ago, there was no official time, and people would just use the sun to tell time. Noon was defined everywhere by when the sun was overhead, and that was good enough.

But, eventually, as trade and international travel became prominent, there needed to be a more standardized way of determining time. And so, in 1675, the Royal Observatory in Greenwich, UK was built, and it was declared that noon in the UK would be officially defined by when the sun is directly overhead of the Greeenwich observatory.

Many other countries quickly followed suite, defining their time zones as offsets of the Greenwich Mean Time (GMT). So, for instance, the U.S. made it’s time zones based on UTC-5, UTC-6, UTC-7, and UTC-8.

Eventually, GMT being used as the basis for all time zones was standardized in 1884. A conference between 26 nations determined that the royal observatory would be the prime meridian of the world. Since there are 24 hours in a day, they decided to divide the world into 24 lines of longitude, each 15 degrees, and each marking the center of a time zone, with one small exception. The final timezone would be split into two areas, each 7.5 degrees, representing +12 and -12.

Of course, these lines are just suggestions, or guides. The conference expected that countries would be able to define their own time zones, but hoped that, for the most part, countries would align with this general principle, of each 15 degree longitude area being a one hour shift.

They likely never expected what would actually come to be. Today, every country in the world has more than one time zone, and there are some really, really weird countries out there.

Weird Time Zones

For instance, take China. If you compared China to lines of longitude, it should probably have 5 time zones. But, ALL of China uses one time zone, Beijing time.

This really, really messes up people living in Western China. For them, sun rise can be as late as 10:30, and sunset is nearly midnight.

In order to deal with this, people in western china will either “unofficially” use UTC+6, or will just adjust their business hours to be something like 11 AM to 9 PM.

This also relates in border weirdness. Crossing the border from China to Afghanistan? You’ll encounter a 3.5 hour time shift. This is the largest time zone change from crossing an international border in the world.

Speaking of .5…

You may notice I said 3.5 hours above. While it is not common, a few countries around the world have decided to have one or more time zones defined to the nearest half hour, rather than hour: Venezuela, Iran, Afghanistan, Sri Lanka, Burma, Newfoundland (in Canada), part of French Polynesia, and Australia.

Why? It’s unclear. But that’s not all. An even smaller number of countries have decide to choose the nearest 15 minute increment time zone. Nepal and the Chatham Islands of New Zealand both have quarter hour time zone divisions.

Australia is having a giggle

Australia having some half hour time zone increments is not the only weird part of the country from a time perspective. Australia is divided into 3 areas of longitude. The west uses UTC+8, the east uses UTC+10, and what does the middle use? UTC+9.5.

That’s right. For some reason, Australia did not decide to universally use half hour increments. Rather, it just yolo’d the middle of the country to use a half hour increment. (A few of Australia’s outlying islands also use half hour time zones).

But Australia’s not done. You see the very bottom right corner of the red area in the Australia map above? Located right on the border between the red and grey is a small town of ~200 people that decided to make their time zone UTC+8:45. This is one of the only cities in the world that decided to use their own time zone different from that of the larger territory.

u wot

But guess what? Everything I have been discussing so far about Australia only considers one part of the year. You see, there is this thing called Daylight Savings Time, and not all regions of Australia use daylight savings time. In fact, only about half do.

Red uses DST, Green doesn’t

As a result, the 3 different time zones in the winter end up becoming 5 different time zones in the summer.

Australia also has a nice little island called “Lord Howe Island”, which uses DST but only advances its clock by half an hour for DST. It is the only country in the world which does not advance by an hour when using DST.

The International Date Line

Australia might have some weird time zones, but trust me when I say that nothing compares to the temporal oddities of the international date line.

As a little bit of context, the international date line is supposed to demarcate the separation between the UTC+12 time zone and the UTC-12 time zone, and should be exactly at 180 degrees longitude, opposite of the prime meridian.

Wouldn’t it be nice if this were the world we lived in

But, of course, it’s never so simple. Since every country chooses its own timezone, in reality the international dateline looks a little something like this.

But, this diagram alone doesn’t really do the dateline justice. So let’s enhance a little.

First, note that it is not at ALL as simple as -12 on the right of the dateline, and +12 on the left of the dateline. Instead, we have islands like the Kiribati islands, which are +14 for some crazy reason. We also have some islands such as American Somoa which are -11 despite being adjacent to the international dateline, and we have multiple islands which are more west of the Kiribati islands, but which are -12 instead of + something.

To put this in a little more perspective, the Kiribati islands are basically at the same longitude as Hawaii, but are OVER 12 hours ahead of Hawaii.

There is another interesting oddity when you consider the timezone map above. Because we have a -12 and +14, this means that every day, briefly, there are three total calendar days active in the world at once. At 10:30 AM on a Wednesday in the UK, it is 11:30 PM on a Tuesday in Niue, and 12:30 AM on Thursday in the Line Islands of Kiribati.

You may ask how on earth we ended up with a +13 and +14 time zone? Well, there is actually a somewhat reasonable historical reason. You see, Kiribati is made of three groups of islands: the Gilbert Islands, the Phoenix Islands, and the Line Islands.

The Gilbert Islands used to be owned by the UK, while the US used to own the Phoneix and Line Islands. At this time, the Gilbert Islands were +12, the Phoenix were -11, and the Line were -10, which made sense since 180 degrees longitude was exactly between the Gilbert Islands and the Phoenix Islands.

But, then the Gilbert Islands gained independence, and eventually the US relinquished control of the Phoenix Islands and Line Islands, causing them to also be considered part of Kiribati. But, now there was a problem. These different islands, which were all part of the same country, wanted to trade. But, trade could really only happen 4 days a week, because the righthand islands were a full day behind the Gilbert islands, and so there were only four days a week when both islands were having a weekday.

As such, Kiribati decided it would make the righthand two islands +13 and +14, instead of having to deal with this messed up trade situation.

The Samoa Swap

Samoa has also had an interesting history with the international dateline. Long ago, it was on the western side of the international dateline. But, in 1892, the US convinced the Samoan king to switch to the eastern side to make trade with the US easier. So, in 1892, Samoa repeated July 4th, allowing it to “shift” its timezone to UTC-11.

But then, in 2011, Samoa split into American Samoa and Western Samoa, and Western Samoa decided it wanted to go back. And so, it switched back to the west of the international dateline, becoming +13 instead of -11. This was done because it’s biggest trading partners are Australia and New Zealand.

The result of this is that by crossing just the 70 km between the two Samoan countries leads you to jump forward (or backwards) 24 hours.


Let’s end with the big daddy of them all, Russia, which has one interesting timezone quirk. Russia has 9 time zones, and yet they all seem to be kind of messed up.

Why? Well Russia used to have 11 time zones, but then decided to switch it to 9 in 2010. Then, in 2011 Russia advanced their clocks forward for DST, but then decided to never switch back. The result? Russia is basically fully offset from the “official” longitude lines by an hour or more everywhere.

Hope you enjoyed this brief tour through time zones.



Davis Treybig
Five Guys Facts

Early stage investor at Innovation Endeavors, former Google PM